The present invention relates to vehicle seats, in particular car seats, including a back that can be folded down onto the seat proper.
More particularly, the invention relates to a vehicle seat comprising:
a seat proper;
a back presenting at least a folding portion capable of pivoting to a limited extent about a first transverse horizontal axis between a raised position for use and a position in which it is folded down forwards;
a rigid plate connecting the folding portion of the back to the seat proper; and
a control mechanism adapted to lock the folding portion of the back either in the raised position or in the folded-down position, said control mechanism including a control piece actuatable by a user to unlock said folding portion of the back.
By way of example, such a seat is described in document EP-A-0 999 092.
In that known seat, the back has two walls and two associated hooks, each wall and its hook serving to lock the back either in the in-use position, or else in the folded-down position. The presence of the two hooks complicates the locking system and the kinematics of the back implies that the back projects rearwards when in the folded-down position.
U.S. Pat. No. 5,393,116 also describes a vehicle seat having a back that can be folded down forwards and a locking mechanism interposed between the seat proper and the back of said seat. The locking mechanism comprises a control piece having an S-shaped guide slot, said control piece being pivotally mounted on the rigid plate which connects the back to the seat proper. That complex locking mechanism also comprises a cam plate interposed between the control piece and the rigid plate, said cam plate also being provided with an S-shaped guide slot which substantially overlies the S-shaped guide slot of the control piece.
A guide peg secured to the back is also received in the respective guide slots of the control piece and of the cam plate.
The locking mechanism described in U.S. Pat. No. 5,393,116 is adapted so that the guide slot of the control piece locks the peg when the back is in its raised position, while the guide slot of the cam plate locks the same peg when the back is in its folded-down position.
That complex locking mechanism thus requires the control piece to be positioned very accurately relative to the cam plate in order to enable the back to be locked in its raised or lowered position, thereby complicating assembly of said locking mechanism on the vehicle seat.
In addition, the presence of two guide slots can cause the peg which is secured to the back to become jammed when the back is in an intermediate position between its raised and lowered positions.
A particular object of the present invention is to mitigate the above-mentioned drawbacks of the prior art.
To this end, according to the invention, the control piece is pivotally mounted on the folding portion of the back about a second transverse horizontal axis parallel to the first axis, said control piece being urged resiliently in a first angular direction about the second axis towards a rest position and being movable by a user in a second angular direction opposite to the first away from its rest position into an actuated position, said control piece having an S-shaped guide slot within which a guide peg secured to the rigid plate is received, said slot comprising:
a curved middle portion adapted to receive the peg when the control piece is in the actuated position, said middle portion being disposed between the first and second axes and extending between first and second ends in the vicinity of which the peg is to be found respectively in the raised position and in the folded-down position of the folding portion of the back, said middle portion of the slot being disposed to extend in a substantially circumferential direction about the first axis when the control piece is in the actuated position;
a first lateral branch which communicates with the first end of the middle portion of the slot and which extends in the second angular direction substantially circumferentially about the second axis to a closed end which is adapted to receive the peg when the folding portion of the back is in the raised position and the control piece is in the rest position, the first branch of the slot being adapted then to lock the folding portion of the back in its raised position; and
a second lateral branch communicating with the second end of the middle portion of the slot and extending in said angular direction substantially circumferentially about the second axis, to a closed end which is adapted to receive the peg when the folding portion of the back is in the folded-down position and the control piece is in the rest position, the second branch of the slot being adapted then to lock the folding portion of the back in the folded-down position.
Because of the disposition of the control means and the shape of its guide slot in combination with the way the slot moves relative to the peg, the user can fold the back down onto the seat and lock it, or can raise the back, and lock it, by acting on a single control member in a single drive direction.
In preferred embodiments of the invention, use may optionally be made of one or more of the following dispositions:
the middle portion of the slot is circularly arcuate in shape, being centered on the first axis when the control piece is in its actuated position;
the end of the second lateral branch of the slot co-operates with the middle portion of the slot to define a catch which comes into contact with the peg when the folding portion of the back is in its folded-down position and the control piece is in its rest position, said catch being shaped to bear against the peg and prevent said peg from sliding into the middle portion of the slot when the folding portion of the back is urged towards its raised position;
the lateral branches of the slot are disposed so as to extend substantially radially relative to the first axis of rotation in opposite directions from said middle portion of the slot when the control piece is in the actuated position;
the control piece comprises a guide member for co-operating with a guide surface formed on the rigid plate to enable the peg to be substantially centered within the guide slot of the control piece when said control piece is in its actuated position;
the guide surface of the rigid plate is defined between two notches in which the guide member of the control piece is received when the folding portion of the back is in its raised position or its folded-down position so as to enable the control piece to be urged resiliently into its rest position; and
the distance measured between the first axis of rotation and the base of either one of the lateral branches of the guide slot corresponds to substantially the distance as measured between said first axis of rotation and the end of the other lateral branch of said slot.